Game Development Reference

In-Depth Information

Complete the table by performing the inversion calculation process for the flows leav-

ing each state on the TFD. Go from state to state and fill in the table as you go along.

Start at the top of the diagram with the
NoPointsItemLocked
state. Do inversion calcula-

tion for flows 3 and 14. Since these flows have the identical value of 50%, there's no

need to do any math. The inverted result in this case is the same as the original. Put

50's in the table for these flows, as shown in Figure 12.23.

Figure 12.22
Inverted flow usage table

initialized with Enter and

Exit flow data.

Figure 12.23
Fixed usage added

for flows leaving

NoPointsItemLocked
.

Moving clockwise around the diagram, do the inversion for flows 2 and 4 coming

from
HavePointsItemUnlocked
. There are only two values, so you can swap values without

having to do a calculation. Figure 12.24 shows the 90% inverted usage for flow 2 and

the 10% inverted usage for flow 4 added to the table.

The next state on your trip around the TFD is
HavePointsItemUnlocked
. This is the state

that has the Exit flow, which is already recorded as 10% in the inverted table. The trick

here is to invert the other flows from this state while preserving the total usage of

100% when they are all added up, including the Exit flow. Have you figured out how

to do this? For step 1, only calculate the reciprocals of flows 5 (5%), 7 (75%), and 12

(10%). These would be 20, 1.33, and 10, respectively. The sum of the reciprocals (step

2) is 31.33. Divide each reciprocal with the sum (step 3) to get 0.638, 0.042, and 0.319.

Since it has already been established that flow 6 (Exit) accounts for 10% of the usage

probability total for
HavePointsItemUnlocked
, then these other three flows must account